This invention relates generally to a sealed door construction and more particularly to a two-pane, door construction used to seal a firebox opening.
The invention is particularly applicable to a curved, two-pane, sealed glass door in combination with a sealed firebox opening for fireplace inserts, free-standing woodburning stoves and the like. However, it is to be appreciated that the invention has broader applications and need not be used as a firebox door but could find particular application as an oven door for a cooking stove or range.
All fireplaces and woodburning stoves, whether of a free-standing nature or otherwise, have a firebox for burning wood and other combustibles. All fireboxes have an opening through which wood, coals and the like are loaded. Firebox inserts and free-standing woodburning stoves and the like which have been designed to be highly efficient require that the firebox opening be sealed so that primary and secondary combustion air can be accurately drawn into the firebox to insure thorough combustion. An example of a fireplace insert using a configured firebox to achieve thorough combustion without the necessity of a catalytic converter or afterburner is disclosed in my prior U.S. Pat. No. 4,672,946 which issued June 16, 1987, entitled "Secondary Combustion Device for Woodburning Stove" incorporated herein by reference.
In all such applications, including those utilizing catalytic converters or afterburners, the firebox is hotter than that which occurs in a conventional, open fireplace. Thus, it is important that the sealed door arrangement for such efficient fireplaces be insulated to minimize accidental burning or singing of the user when loading fuel into a hot firebox. At the same time, it is extremely important to fireplace owners that the design of the door be aesthetically pleasing and blend into the surroundings of the room where the fireplace or stove is situated.
Glass pane doors have traditionally been used to close the firebox opening. Typically, such doors are of single pane construction although the glass used has been "smoked" or "blackened" and is tempered or heat resistant. In the "hot" firebox applications described, the glass door construction typically frames the entire pane about its inside and outside peripheral surfaces to secure an adequate seal for the glass. It has been found that when, for aesthetic reasons, a glass curved door is desired for a firebox opening, a sealed door cannot be provided. Typical fireplace openings require a curved surface defined by radius of about 30-36 inches. Tempered, heat-resistant curved glass in such sizes have variations in their radius of curvature of as much as 11/2 inches and it has not been possible to construct a frame which seals the inside and outside surfaces of the curved glass about its periphery given such variations. The problem is further aggravated by the natural expansion of the glass as it is exposed to the heat from the firebox. Additionally, the glass must meet certain safety requirements for firebox openings.
Further complicating the door construction is the fact that the door(s) for the firebox opening are large and the weight of the glass panes make the door heavy. This subjects the door hinge and the door opening seal arrangement, which must be adjustable, to a severe operating environment that tends to loosen such adjustments and skew the door(s) within its opening. Heretofore, skewing of the door tended to unseat the seal for the door opening thus leaking air, in an uncontrolled manner into the firebox adversely affecting thorough combustion.